.TH "seccomp_init" 3 "25 July 2012" "paul@paul-moore.com" "libseccomp Documentation"
.\" //////////////////////////////////////////////////////////////////////////
.SH NAME
.\" //////////////////////////////////////////////////////////////////////////
seccomp_init, seccomp_reset \- Initialize the seccomp filter state
.\" //////////////////////////////////////////////////////////////////////////
.SH SYNOPSIS
.\" //////////////////////////////////////////////////////////////////////////
.nf
.B #include <seccomp.h>
.sp
.B typedef void * scmp_filter_ctx;
.sp
.BI "scmp_filter_ctx seccomp_init(uint32_t " def_action ");"
.BI "int seccomp_reset(scmp_filter_ctx " ctx ", uint32_t " def_action ");"
.sp
Link with \fI\-lseccomp\fP.
.fi
.\" //////////////////////////////////////////////////////////////////////////
.SH DESCRIPTION
.\" //////////////////////////////////////////////////////////////////////////
.P
The
.BR seccomp_init ()
and
.BR seccomp_reset ()
functions (re)initialize the internal seccomp filter state, prepares it for
use, and sets the default action based on the
.I def_action
parameter.  The
.BR seccomp_init ()
function must be called before any other libseccomp functions as the rest
of the library API will fail if the filter context is not initialized properly.
The
.BR seccomp_reset ()
function releases the existing filter context state before reinitializing it
and can only be called after a call to
.BR seccomp_init ()
has succeeded.
.P
When the caller is finished configuring the seccomp filter and has loaded it
into the kernel, the caller should call
.BR seccomp_release (3)
to release all of the filter context state.
.P
Valid
.I def_action
values are as follows:
.TP
.B SCMP_ACT_KILL
The thread will be terminated by the kernel with SIGSYS when it calls a syscall
that does not match any of the configured seccomp filter rules.  The thread
will not be able to catch the signal.
.TP
.B SCMP_ACT_TRAP
The thread will be sent a SIGSYS signal when it calls a syscall that does not
match any of the configured seccomp filter rules.  It may catch this and change
its behavior accordingly.  When using SA_SIGINFO with
.BR sigaction (2),
si_code will be set to SYS_SECCOMP, si_syscall will be set to the syscall that
failed the rules, and si_arch will be set to the AUDIT_ARCH for the active ABI.
.TP
.B SCMP_ACT_ERRNO(uint16_t errno)
The thread will receive a return value of
.I errno
when it calls a syscall that does not match any of the configured seccomp filter
rules.
.TP
.B SCMP_ACT_TRACE(uint16_t msg_num)
If the thread is being traced and the tracing process specified the
.B PTRACE_O_TRACESECCOMP
option in the call to
.BR ptrace (2),
the tracing process will be notified, via
.BR PTRACE_EVENT_SECCOMP ,
and the value provided in
.I msg_num
can be retrieved using the
.B PTRACE_GETEVENTMSG
option.
.TP
.B SCMP_ACT_ALLOW
The seccomp filter will have no effect on the thread calling the syscall if it
does not match any of the configured seccomp filter rules.
.\" //////////////////////////////////////////////////////////////////////////
.SH RETURN VALUE
.\" //////////////////////////////////////////////////////////////////////////
The
.BR seccomp_init ()
function returns a filter context on success, NULL on failure.  The
.BR seccomp_reset ()
function returns zero on success, negative errno values on failure.
.\" //////////////////////////////////////////////////////////////////////////
.SH EXAMPLES
.\" //////////////////////////////////////////////////////////////////////////
.nf
#include <seccomp.h>

int main(int argc, char *argv[])
{
	int rc = \-1;
	scmp_filter_ctx ctx;

	ctx = seccomp_init(SCMP_ACT_KILL);
	if (ctx == NULL)
		goto out;

	/* ... */

	rc = seccomp_reset(ctx, SCMP_ACT_KILL);
	if (rc < 0)
		goto out;

	/* ... */

out:
	seccomp_release(ctx);
	return \-rc;
}
.fi
.\" //////////////////////////////////////////////////////////////////////////
.SH NOTES
.\" //////////////////////////////////////////////////////////////////////////
.P
While the seccomp filter can be generated independent of the kernel, kernel
support is required to load and enforce the seccomp filter generated by
libseccomp.
.P
The libseccomp project site, with more information and the source code
repository, can be found at https://github.com/seccomp/libseccomp.  This tool,
as well as the libseccomp library, is currently under development, please
report any bugs at the project site or directly to the author.
.\" //////////////////////////////////////////////////////////////////////////
.SH AUTHOR
.\" //////////////////////////////////////////////////////////////////////////
Paul Moore <paul@paul-moore.com>
.\" //////////////////////////////////////////////////////////////////////////
.SH SEE ALSO
.\" //////////////////////////////////////////////////////////////////////////
.BR seccomp_release (3)

